Internal combustion engine



FIG. 1 is a front view of internal-combustion engine, showing my new design;

FIG. 2 is a rear view thereof;

FIG. 3 is a top view thereof;

FIG. 4 is a right side view thereof;

FIG. 5 is a left side view thereof;

FIG. 6 is a perspective view thereof; and,

FIG. 7 is another perspective view thereof. 

The ornamental design for an internal combustion engine, as shown and described. 